Biomedical Engineering Reference
In-Depth Information
complicated physiological conditions because of premature disintegration of
the micelle structure due to enzymatic degradation and the burst release of
drug absorbed on the surface of the micelle core. It is desirable to construct
polymeric micelle-based drug carriers with superior structures that can
enhance their ability to control the drug release profiles. Two kinds of
complex micelles, either with a core-shell-corona (CSC) structure or with
surface channels, were developed recently for the above purpose. Though a
hydrophobic drug can be easily encapsulated in the micelle core during
micellization, it is difficult to encapsulate hydrophilic or ionic drugs in
hydrophobically associated micelles due to the lack of strong interaction.
Polyion complex (PIC) micelles were developed for the incorporation of
hydrophilic or ionic drugs and a series of studies on drug delivery by PIC
micelles has been reported. This chapter will discuss recent advances in drug
delivery by complex micelles.
d
n
4
y
3
n
g
|
7
9.2 Core-Shell-Corona Micelles for Drug Delivery
Core-shell-corona micelles have an onion structure and can be obtained by
self-assembly of a triblock copolymer or two diblock copolymers. Gohy et al.
2
reported the formation of three-layer micelles by the triblock copolymer
polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-b-P2VP-
b-PEO) in aqueous solution. These micelles are referred to as core-shell-corona
(CSC) micelles with PS as the core, P2VP as the shell, and PEO as the corona.
Zhang et al.
3
also reported CSC micelles with a thermo-responsive shell self-
assembled by the triblock copolymer poly(ethylene glycol)-b-poly(N-isopropy-
lacrylamide)-b-polystyrene (PEG-b-PNIPAM-b-PS) in aqueous solution. In
addition to self-assembly of triblock copolymers, CSC micelles can also be easily
prepared by adsorption of block copolymer chains onto the core-shell micelles
through hydrogen bonding or electrostatic interaction (Figure 9.1).
4-6
Figure 9.1
Schematic formation of CSC complex micelles formed by adsorption of a
block copolymer onto core-shell micelles via hydrogen bonding.
4
